This invention relates to semiconductor devices and methods of manufacturing the same, and more particularly, to semiconductor light emitting devices and methods of manufacturing the same.
Light emitting diodes and laser diodes are well known solid state lighting elements capable of generating light upon application of a sufficient current. Light emitting diodes and laser diodes may be generally referred to as light emitting devices (“LEDs”). Light emitting devices generally include a p-n junction formed in an epitaxial layer grown on a substrate such as sapphire, silicon, silicon carbide, gallium arsenide and the like. The wavelength distribution of the light generated by the LED generally depends on the material from which the p-n junction is fabricated and the structure of the thin epitaxial layers that make up the active region of the device.
Typically, an LED chip or die includes a substrate and a diode region including an n-type layer, a p-type layer and a p-n junction. The diode region may be epitaxially formed on a substrate, such as a sapphire, silicon, silicon carbide, gallium arsenide, gallium nitride, etc., growth substrate, but the completed device may not include a substrate. The diode region may be fabricated, for example, from silicon carbide, gallium nitride, gallium phosphide, aluminum nitride and/or gallium arsenide-based materials and/or from organic semiconductor-based materials. An anode contact may ohmically contact the p-type layer of the device (typically, an exposed p-type epitaxial layer) and a cathode contact may ohmically contact an n-type layer of the device (such as the substrate or an exposed n-type epitaxial layer).
When a potential is applied to the contacts, electrons may be injected into the active region from the n-type layer and holes may be injected into the active region from the p-type layer. The radiative recombination of electrons and holes within the active region generates light. Some LED chips include an active region with multiple light emitting regions or active layers (also known as multi-quantum-well structures) between or near the junction of the n-type and p-type layers. The light radiated by the LED may be in the visible or ultraviolet (UV) regions, and the LED may incorporate wavelength conversion material such as phosphor.
LEDs are increasingly being used in lighting/illumination applications, with a goal being to provide a replacement for the ubiquitous incandescent light bulb.